1. Field of the Invention
The present application relates to optical data transmission, and more particularly to converting parallel electronic signals to optical signals and wavelength multiplexing those signals in parallel over optical fiber and converting back to parallel electronic signals.
2. Background Information
Transmitting parallel data over wire cables usually entails using many conductors (copper wires). In these cases, EMI (electromagnetic interference), ground loops, and reliability issues must be considered by designers. This is especially true where the wires comprise part of a hinge, e.g., in flip or clam shell type of cell phone, or “flip phone”). One approach to these issues has been to serialize the data and de-serialize it at the receiver. The number of wires in the cable is reduced, but timing and complex circuitry issues are introduced.
WDM (Wavelength Division Multiplexing) allows a number of different light wavelengths or frequencies or “colors” to be sent down a single optical fiber cable. Lasers provide a single wavelength signal and many such signals can travel in the same optical fiber with no interference with each other. Known system have transferred 100 or more simultaneous optical signals, each at a data rate of more than 10 gigabits per second, over a cable 250 miles long.
LEDS (light emitting diodes) output a narrow band of wavelengths that may be tens or more nanometers wide compared to less than 0.1 nanometers for lasers) that may also be multiplexed over an optical cable. The form factor of LEDs (smaller, using less power, more suitable for integration on a chip) may suggest their use for hand held mobile devices, e.g., cell phones.
There is a laser producing diode (ILD—injection-laser diode) that may be used in some applications.
WDM eliminates EMI, serialization/de-serialization, and employs a single optical fiber cable.